1. Field of the Invention
The present invention relates to a communication device. More particularly, the present invention relates to calibration in a communication device.
2. Description of the Related Art
In recent years, there is a trend of supporting multi-band and multi-mode, and concurrently minimizing cost and power consumption, in a mobile communication system. To meet this trend, a transceiver structure of a Mobile Station (MS) may use a direct conversion scheme. A transceiver employing the direct conversion scheme has a simple structure, and has an advantageous feature in size and cost, and has a reconfigurable structure that is easy to use. However, the direct conversion scheme has a characteristic of being sensitive to circuit impairment such as In-phase/Quadrature-phase (IQ) mismatch, Transmitter Local Oscillator (TX LO) feed-through, RX Direct Current (DC)-offset and the like. The imperfection of the aforementioned Radio Frequency (RF) processing means is one cause of transceiver performance deterioration. Accordingly, calibration is performed to compensate for the aforementioned imperfection.
Also, as the commercialization of a next-generation system having a high data rate makes progress, a transceiver supporting the high data rate is being developed. To provide the high data rate, the transceiver requires lower Error Vector Magnitude (EVM) performance than a legacy system. To meet the low EVM, a distortion of the transceiver generated while a signal goes through the whole system should be minimized. The distortion of the transceiver results in the deterioration of a Signal to Noise Ratio (SNR) of a signal. Mostly, the distortion of the transceiver is generated while a signal goes through an analog and RF circuit. In order to remove the impairment of the analog and RF circuit to guarantee performance, calibration for the analog and RF circuit is performed.
In general, the calibration for the analog and RF circuit is controlled in a digital block processing a digital signal. For instance, the digital block includes a modulator/demodulator (modem). For example, the calibration for the analog and RF circuit is carried out by a control signal from the modem, in a state where the analog and RF circuit and the modem interwork with each other. In this case, it is difficult to achieve an accurate measurement for analog and RF circuit performance, because self-calibration of a chip level including the analog and RF circuit is not performed. Accordingly, when the analog and RF circuit goes beyond a performance difference assumed as a margin upon interworking with the modem, in other words, when the calibration for the analog and RF circuit is performed in a situation where the analog and RF circuit and the modem interwork with each other, there is a possibility that a situation occurs in which the performance of the analog and RF circuit does not meet the required system standard. Also, the calibration for the analog and RF circuit performed in a state where the analog and RF circuit and the modem interwork with each other consumes a relatively higher cost than a test at a chip level.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.